$4x^2-7a^2+5x^2+a^2$

$\frac{dx}{dt}=t^2+t^2x$

$\frac{cos\left(x\right)}{1+\cos\left(x\right)}+\frac{\cos\left(x\right)}{1-cos\left(x\right)}=2\:cot\left(x\right)\:x\:csc\left(x\right)$

$\frac{d^3y}{dx^3}\left(\frac{2}{15}x^6-\frac{2}{9}+\frac{5}{3}x^3\right)$

$3x-1\ge7x+7$

$-4\left(3x-3\right)+9\:\left(x+1\right)$

$\left(\sqrt{7}+2\right)\left(\sqrt{7}-2\right)$